﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;


public static class StringExtentionClass
{
    public static string ToUpperFirestLetter(this string str)
    {
        if (str.Length == 0 || str == null)
        {
            throw new ArgumentNullException("Empty string"); 
        }
        StringBuilder result = new StringBuilder(str.Substring(0, 1).ToUpper());
        result.Append(str.Substring(1));
        return result.ToString();
    }
}

